Inflammation and post-operative recovery in patients undergoing total knee arthroplasty-secondary analysis of a randomized controlled trial

Objective: Reduced function persists for many patients after total knee arthroplasty (TKA). Inflammation is part of osteoarthritis' pathophysiology, and surgery induces a marked inflammatory response. We therefore wanted to explore the role of inflammation in long-term recovery after TKA, and thus conducted this secondary analysis of our randomized controlled trial (RCT) of physical rehabilitation +/- progressive strength training (PST). We aimed to investigate whether (1) inflammation is associated with functional performance, knee-extension strength, and knee pain before TKA; (2) PST affects inflammation, and the inflammatory state over time; (3) baseline or surgery-induced inflammation modifies the effect of rehabilitation +/- PST on change in 6-min walk test (Delta 6MWT); and (4) baseline or surgery-induced inflammation is associated with D6MWT following TKA. Design: In the primary trial report's per-protocol analysis, 72/82 patients were included. Sixty had >= 1 blood sample before and after TKA, and were included in this secondary analysis. Inflammation was measured by interferon gamma-inducible protein (IP)-10, soluble urokinase plasminogen activator receptor (suPAR), interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-alpha at baseline; day 1, week 4, 8, and 26 after TKA. Results: At baseline, suPAR (P = 006) was negatively associated with 6MWT. Neither baseline nor surgery-induced inflammation modified the response to rehabilitation +/- PST. Only surgery-induced IL-10 was associated with Delta 6MWT(26 weeks-baseline) (P = 0.001), also adjusted for 6MWTbaseline, age, sex and body mass index (BMI). Conclusion: In this secondary analysis, only increased surgery-induced IL-10 response was associated with decreased long-term functional performance after TKA. The importance of controlling the surgery-induced immune response remains to be investigated further. (C) 2017 Osteoarthritis Research Society International. Published by Elsevier Ltd. All rights reserved.